Some might say the answer to my question is trial and error but I woud like to get as much error out of the way as possible before trial so I was hoping to get some resources regarding illumination for panels and buttons. I'm trying to figure out what sort of LED's to use, how to space them etc to get an even distribution of light.

I know it's dependent on the materials used and the like but I was wondering whether there's any rules of thumb? My main concern is the fact that a button which sits on a switch of some sort... will by that very virtue have less light due to the switch blocking it off than other areas. So for such things as MCDU/FMC buttons, you would have dead spots right in the centre of the buttons where the contact patch is?

The thing I can't quite get my head around is how much light can travel through clear objects i.e. if you have a light soruce say 2cm away from a button... part of the light will hit the button (what little area is left which isn't in contact with an opaque switch) and then dissipate throughout the button making it all light up without any dead spots. So that's my main concern I think.